Gravitational Waves: The Pulsar Connection

by Paul Gilster on March 25, 2009

I, for one, would like to be in on the detection of gravitational waves. They flow naturally from the theory of General Relativity and ought to be out there, but none have ever been directly detected. What might make finding them easier would be a spectacular event, such as the merger of a pulsar and a neutron star or a black hole, an event that should cause a huge emission of gamma rays in its final moments. Short-period binaries are the ticket — find them and you have the chance to test General Relativity to high degrees of precision.

Some 200,000 volunteers have already signed up for the EINSTEIN@Home project, which searches for gravitational waves from rapidly spinning neutron stars. The project is now looking for volunteers for its new search, one that will use home computers to analyze data gathered at the Arecibo Observatory in Puerto Rico in the hunt for binary radio pulsars.

This is jazzy stuff, another opportunity, like SETI@Home and the Galaxy Zoo, for those of us with an astronomical bent to deploy our computing cycles productively. And what could be more exotic? Gravitational wave detection takes us into fundamental questions about the physics of gravity and may offer new tools for astronomical observations. Think of these waves as ripples in spacetime emitted by accelerating masses, an analog to the way accelerating charges produce electromagnetic waves.

Test General Relativity’s prediction that these waves propagate at the same speed as light, and that the graviton (the fundamental particle that accompanies these waves) has zero rest mass.

Test General Relativity’s prediction that the forces the waves exert on matter are perpendicular to the waves’ direction of travel, and stretch matter along one perpendicular direction while squeezing it along the other; and also, thereby, test General Relativity’s prediction that the graviton has twice the rate of spin as the photon.

Firmly verify that black holes exist, and test General Relativity’s predictions for the violently pulsating space-time curvature accompanying the collision of two black holes. This will be the most stringent test ever of Einstein’s General Relativity theory.

We’ve come to realize how effective distributed computing can be. A Cornell University news release points out that current searches of radio data are ineffective for pulsars in binary systems with orbital periods less than fifty minutes. The EINSTEIN@Home project will put enough computational power onto the job that we can begin to detect systems with much shorter periods, down to a brief eleven minutes. We’ll wind up with better estimates of binary system formation and disappearance in such scenarios, along with precisely identified targets for gravitational wave detectors.

From a propulsion standpoint, what intrigues us is that a deeper understanding of gravity and its coupling with electromagnetism could point to a theoretical basis for manipulating inertia or gravity itself. Mass, after all, warps the spacetime against which electromagnetism is measured. Now we’ve moved a long way from the original gravitational wave detection, and haven’t begun to get into the question of energy requirements that could render such thoughts chimerical, but finding gravitational waves takes us deeper into this force’s rich mysteries.

The evidence for gravity waves is pretty sound (based on indirect observation), though it would be quite awesome to actually detect them. Not least because of the information we might be able to gather.

It’s a remarkable prospect, and may or may not be possible to achieve one day. One of the drivers for the formation of the Tau Zero Foundation was the premise that a rigorous investigation into matters like this would either reveal new possibilities or else help us understand why things like controlling inertia are not possible. Either way it’s an investigation worth making, the key being to learn more about the universe. But, of course, the hope is that some clue to advanced propulsion will flow from these studies. Finding out for sure is probably going to be a matter for more than a single generation.

guys… the above comments are really GREAT!!! yeah you bet A GRAVITY DRIVE!!!!!! i played around with an idea like that quite some time ago however in the end nobody could come up with any idea as to how to really do it ! this is the perfect (or one of them),subject for tau zero to look into! a very exciting prospect! hope i will read alot more before this thread runs its course.maybe tadaaa!!!!!!!!! even this time someone will come up with THE idea! thank you robin thank you rob thank you paul george

An awesome technology would be one that can convert gravitational charge into electrical charge and visa versa. The ability to convert electrical charge into uncharged mass or into nuclear force or QCD color force charge would likewise be awesome.

The ability to transmute gravity waves or gravitons into electromagentic waves and photons would be a wonderfull also.

The ability to convert gravity waves or gravitons into gluons and/or weak force bosons is also interesting to consider.

Also on the list of extremes would be the ability to convert inertial mass into electrical charge, QCD color force charge, weak force bosons, gluons, Higgs field bosons. photinos, gluinos, gravitinos, Higgsinos, winos, sleptions, squarks, sneutrinos and the like. and visa versa.

Now one might argue that these above conservative fields only exist because they have embodying mass or energy particles. However due to field mixing parameters such as the electroweak mixing paramater, the electrostrong, electro-weak-strong, electro-gravatic, electroweak-gravatic, and electro-weak-strong-gravatic mixing parameters should also exist due to GUT theories and theories of everything.

Perhaps some net field force quantities can be transformed. Converting a net electrical charge for instance into gravitational charge would seem to violate the laws of conservation of electrical charge, however, perhaps the entire universe or multiverse is one mainly large free lunch.

I like the idea of the gravitational wave reflection concepts pointed out by Robin Goodfellow in Technology Review. A study of gravitational wave minipulation by electrodynamic systems might point the way to electrogravatic propulsion systems and a means to unify gravitation with electromagnetism: something Einstein tried to accomplished but had no sucess at.

gentlemen,as always some real good ideas have been expressed above by jim and everybody else but the fact remains,how to do it!? we should all give that some real thought in the days ahead.where to begin? not so easy a subject. respectfully guys your friend george

There are those who are concerned that since we have not detected gravitational waves from local sources, perhaps these waves do not actually exist. And then are those who remain skeptical because LIGO has not made a detection of GWs from the supposedly myriad of sources capable of generating them elsewhere. Now, my background is in the life sciences and chemistry so I feel as though I am not in a position in terms of knowledge or experience to evaulate the validity of these skeptical positions. Thus, my question to those of you posting in this thread is this:

Is the present absence of a detection of GWs a serious threat to the theory that posits their existence, or, alternatively, will it take more years (say, 5 or 10) before the aforementioned skeptics’ point of view be seen as a good point/cause for concern in the physics community?

spaceman, certainly the theory will be under threat if we never detect gravitational waves, but my sense is that at present many theorists are fairly sure a detection will not be far off. Others will have a more informed opinion on this than I do, but I would go along with the notion that the five or ten more years you mention and possibly more are a reasonable period of time to expect a detection, and we’ll see what happens after that. Anyone else?

george, re your comment on what to do next, the answer from my perspective is to keep reporting on and studying the solid, peer-reviewed work that is being done and is being kept visible so that other scientists can weigh lab results and reproduce them. Some of these issues were studied by the Breakthrough Propulsion Physics project, and in Frontiers of Propulsion Science, Eric Davis has a good chapter summarizing that and later work. Getting lab investigations into the public process of science, as Martin Tajmar continues to do, advances our knowledge. For theories to emerge with any credibility, their creators have to engage in this process and meet the test of study and reproducible results. Preprint sites like arXiv are a wonderful aid in helping us watch this at work as it develops.

Regarding Electrodynamic Gravity Field Minipulation technologies that could come about through the study of gravity waves, the consideration of any future varified GUT and TOE theories would be unified field theories on steriods.

Another interesting consequence regarding unifications could be the development of hybrid force technologies from future publically known nuclear and sub-nuclear physics research that would permit an attractive or repulsive force between a massive base force emmitter and a space craft with the same force of attraction or repuslsion acting on a given ship based nucleon as that which acts between nucleons within the atomic nucleus.

Perhaps some sort of electrostrong mixing parameter can be utilized to produce such a hybrid force. Alternatively, perhaps some sort of gravato-strong mixing parameter can permit the development of a long range gravity like propulsive forces that acts on the ship on a per nucleon basis, with the strength of the strong nuclear force that binds the atomic nucleons together in the atomic nucleous.

Now the force that acts between quarks grows to a limiting but extremely high value as the quarks are pulled apart. Eventually, the nuclear force field lines or the strong-gluon-mediated-force field lines become so strained that the quark binding energy is transformed into new quarks. This is a reason why seperate quarks are rarely seen. Note that it was only within the past week or so that seperate quarks were reported as having been detected.

In short, grand unified field theories and theories of every thing might enable us to create hybrid forces and hybrid particles and hybrid force mediating quanta, as well as perhaps some sort of hybrid space time form analogues.

I think that it would be awesome if some extreme gamma factor space craft traveling inertially through space time from our century or from the following next few centuries as developed by free and open private enterprize would simply show up at some black government facility 10 EXP 13 years into the future. Perhaps such a vehicle would have been long forgotten in the annuals of 10 EXP 13 years of history. I can imagine the freakout such a event could cause our cosmically future distant descendents if a a vehicle with a NASA logo, and ESA logo, a Virgin Galactic logo or the like suddenly showed up after 10 trillion year.

George, my thinking is thus in a nut shell, keep being a practicioner of Tau Zero and dream the dreams of What Dreams May Come. If we dream it, perhaps in the next century or so, They Will Build It.

paul,jim,all my friends above…yes i will attempt to read more on the subject but quite ironically i had an idea yesterday that i had come here to discuss at this very “sign on” : it seemed to me upon further thought that no matter where we are in the galaxy we are actually immersed in a sea of gravity.yes sometimes stonger sometimes weaker but no doubt (unless someone can correct me) ,always there to a greater or lessor extent.maybe we could learn a method by which we could use its omnipresent power to “pull ourselves along” sort of like the way a fish utilizes the water into which it is immersed for its own propulsion.maybe powerful interacting fields switching on and off several times a second and generated aboard our space craft could fit the bill ?! “just” an other way of putting forth one of my favorite all time theories – that of using space itself for propulsion ! i know that nasa’s bpp project had a look at that. if mark millis should happen along and by chance read the above i would love to read his comments.but really seriously eveybody – what do you think? very respectfully to one of the best groups of minds i have ever had the opportunnity of discussing these subjects with – your friend george scaglione

Thanks for the above response and comments and, Paul thanks for providing the above NASA link. I just spent the last half hour browzing through it an reading some of it. I will go back there sometime tomorrow.

George;

Your mentioning of the concept of using a means to react against the ambient interstellar gravity fields reminds my of a turboprop aircraft. What if some sort of rotor or turbine system could churn through the ambient gravity fields or perhaps even through the various zero point fields like an arcraft prop, a turbofan jet engine, or an ocean going ship based propeller.

It might even be the case that a propellar, if it was rotating fast enough, could propell itself foward by pushing against the ambient star light and CMBR energy.

Note that I am going to take a couple day break from Tau Zero since I think I am posting perhaps to frequently. Anyone else, feel free to chime in.

I can become carried away like a kid in a candy shop when it come it interstellar propulsion.

Abstract: Short Gamma Ray Bursts (SGRB) are believed to originate from the merger of two compact objects. If this scenario is correct, SGRB will be accompanied by the emission of strong gravitational waves, detectable by current or planned GW detectors, such as LIGO and Virgo. No detection of a gravitational wave has been made up to date.

In this paper I will use a set of SGRB with observed redshifts to fit a model describing the cumulative number of SGRB as a function of redshift, to determine the rate of such merger events in the nearby universe. These estimations will be used to make probability statements about detecting a gravitational wave associated with a short gamma ray burst during the latest science run of LIGO/Virgo.

Chance estimations for the enhanced and advanced detectors will also be made, and a comparison between the rates deduced from this work will be compared to the existing literature.

The radio signals produced by passing gravitational waves could make them easier to detect

Wednesday, May 20, 2009

Any time now, the folks at the gravitational wave detector LIGO expect to come across conclusive evidence that their search is over. If the theorists have their numbers right, the machine should spot a passing gravitational wave sometime in the next year or so.

LIGO works by watching for the tell-tale squeezing and stretching of space as gravitational waves pass by. But might there be another way to spot these waves?

For some 40 years now, various physicists have pointed out that gravity waves ought to produce electromagnetic waves. Today, Peter Hogan and Shane O’Farrell at University College Dublin in Ireland resurrect the idea.

“About 1 per cent of the noise you see on the screen of a badly-tuned analogue TV is the cosmic background radiation — the echo of the Big Bang. Wouldn’t it be cool to know that your old Sony Trinitron could also tune into the sound of black holes colliding.”

Abstract: We show that the Big Bang Observer (BBO), a proposed space-based gravitational-wave (GW) detector, would provide ultra-precise measurements of cosmological parameters. By detecting ~300,000 compact-star binaries, and utilizing them as standard sirens, BBO would determine the Hubble constant to 0.1%, and the dark energy parameters w_0 and w_a to ~0.01 and 0.1,resp. BBO’s dark-energy figure-of-merit would be approximately an order of magnitude better than all other proposed dark energy missions.

To date, BBO has been designed with the primary goal of searching for gravitational waves from inflation. To observe this inflationary background, BBO would first have to detect and subtract out ~300,000 merging compact-star binaries, out to z~5. It is precisely this foreground which would enable high-precision cosmology. BBO would determine the luminosity distance to each binary to ~percent accuracy.

BBO’s angular resolution would be sufficient to uniquely identify the host galaxy for most binaries; a coordinated optical/infrared observing campaign could obtain the redshifts. Combining the GW-derived distances and EM-derived redshifts for such a large sample of objects leads to extraordinarily tight constraints on cosmological parameters. Such “standard siren” measurements of cosmology avoid many of the systematic errors associated with other techniques.

We also show that BBO would be an exceptionally powerful gravitational lensing mission, and we briefly discuss other astronomical uses of BBO.

Abstract: The goal of the Laser Interferometric Gravitational-Wave Observatory (LIGO) is to detect and study gravitational waves of astrophysical origin. Direct detection of gravitational waves holds the promise of testing general relativity in the strong-field regime, of providing a new probe of exotic objects such as black hole and neutron stars, and of uncovering unanticipated new astrophysics.

LIGO, a joint Caltech-MIT project supported by the National Science Foundation, operates three multi-kilometer interferometers at two widely separated sites in the United States. These detectors are the result of decades of worldwide technology development, design, construction, and commissioning. They are now operating at their design sensitivity, and are sensitive to gravitational wave strains smaller than 1 part in 1E21.

With this unprecedented sensitivity, the data are being analyzed to detect or place limits on gravitational waves from a variety of potential astrophysical sources.

Abstract: The vertical structure of temperature observed by SABER (Sounding of Atmosphere using Broadband Emission Radiometry) aboard TIMED (Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics) and sprites observations made during the Eurosprite 2003 to 2007 observational campaign were analyzed.

Sprite observations were made at two locations in France, namely Puy de Dome in the French Massif Central and at the Pic du Midi in the French Pyrenees.

It is observed that the vertical structure of temperature shows evidence for a Mesospheric Inversion Layer (MIL) on those days on which sprites were observed. A few events are also reported in which sprites were not recorded, although there is evidence of a MIL in the vertical structure of the temperature.

It is proposed that breaking gravity waves produced by convective thunderstorms facilitate the production of (a) sprites by modulating the neutral air-density and (b) MILs via the deposition of energy. The same proposition has been used to explain observations of lightings as well as both MILs and lightning arising out of deep convections.

Abstract: The merger of a super-massive binary black hole (SBBH) is one of the most extreme events in the universe with a huge amount of energy released by gravitational radiation. Although the characteristic gravitational wave (GW) frequency around the merger event is far higher than the nHz regime optimal for pulsar timing arrays (PTAs), nonlinear GW memory might be a critical smoking gun of the merger event detectable with PTAs.

In this paper, basic aspects of this interesting observation are discussed for SBBHs, and the detection numbers of their memory and inspiral GWs are estimated for ongoing and planned PTAs. We find that the expected detection number would be smaller than unity for the two-types of signals even with the Square Kilometer Array.

We also provide various scaling relations that would be useful to study detection probabilities of GWs from individual SBBHs with PTAs.

Abstract: The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) is a consortium of astronomers whose goal is the creation of a galactic scale gravitational wave observatory sensitive to gravitational waves in the nHz-microHz band. It is just one component of an international collaboration involving similar organizations of European and Australian astronomers who share the same goal.

Gravitational waves, a prediction of Einstein’s general theory of relativity, are a phenomenon of dynamical space-time generated by the bulk motion of matter, and the dynamics of space-time itself. They are detectable by the small disturbance they cause in the light travel time between some light source and an observer.

NANOGrav exploits radio pulsars as both the light (radio) source and the clock against which the light travel time is measured. In an array of radio pulsars gravitational waves manifest themselves as correlated disturbances in the pulse arrival times. The timing precision of today’s best measured pulsars is less than 100 ns.

With improved instrumentation and signal-to-noise it is widely believed that the next decade could see a pulsar timing network of 100 pulsars each with better than 100 ns timing precision. Such a pulsar timing array (PTA), observed with a regular cadence of days to weeks, would be capable of observing supermassive black hole binaries following galactic mergers, relic radiation from early universe phenomena such as cosmic strings, cosmic superstrings, or inflation, and more generally providing a vantage on the universe whose revolutionary potential has not been seen in the 400 years since Galileo first turned a telescope to the heavens.

Comments: This document is the NANOGrav consortium’s submission to Astro2010’s Program Prioritization Panel on Particle Astrophysics and Gravitation

Charter

In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For the last seven years, this site has coordinated its efforts with the Tau Zero Foundation, and now serves as the Foundation's news forum. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image: Marco Lorenzi).

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